About 250 million people who live in the Afro-Asian dryland belt face a shortage of water for their entire lives. Hundreds of millions more in less drought-prone regions of the developing world have to cope repeatedly with reduced supplies. A rapid and effective assessment of how to alleviate the shortfall of safe water is therefore vital. In arid and semi-arid areas surface water storage is subject to a greater rate of evaporation than precipitation, so groundwater, hidden beneath the land surface, provides a more assured alternative. Rainwater is also lost by flowing away in streams and rivers far more quickly than in areas with substantial vegetation. Harvesting that otherwise lost resource and diverting it to forms of storage that are secure from evaporation – ideally by using it to recharge groundwater – is an equally important strategy. Securing a sustainable water supply for all peoples is the most important objective that geoscientists can address. Remote sensing combined with an understanding of groundwater storage and surface-water harvesting is a powerful tool for achieving such provision.
Existing geological and topographic maps of many dryland regions lack sufficient detail and accuracy to offer much assistance in water exploration and development. Only a significant increase in the number of geoscientists able to interpret universally available remotely sensed data in a water-supply context can close that knowledge gap fast enough to prevent yet more disasters and to relieve those that are unavoidable. Given basic interpretive skills, free software, digital images and terrain data, all geologists can play a part in mapping the necessary detail, thereby helping to improve the lives of local and regional populations.
This course aims at providing a hydrogeological and remote sensing background for groundwater exploration. Its target users are: geoscience professionals in national surveys; independent consultants; senior undergraduates in university geology departments; and engineers working in the WASH or WatHab sections of NGOs and international agencies. It is in two parts: one covers scientific and technical background, the other offers some practical experience with image processing and mapping software.
Theoretical issues are covered by 6 comprehensively illustrated chapters:
- Chapter 1 introduces different kinds of target for groundwater development and their geological and terrain attributes;
- Chapter 2 summarises important principles underlying the capture of remotely sensed data at different wavelengths throughout the electromagnetic spectrum, and the way in which materials that make up the Earth’s surface interact differently with various kinds of radiation. This multispectral approach is the basis for developing image interpretation strategies that serve to distinguish vegetation; rocks, soils and the minerals in them; and moisture.
- Chapter 3 focuses on the most important aspect of image interpretation: visualising the links between topographic terrain and the geology that underpins it. It uses stereoscopic aerial photography in anaglyph format to show the advantages of photogeology;
- Chapter 4 reveals a wider context for some of the areas covered by Chapter3, supported by geological maps that reinforce the links between terrain and geology, which is where the super-synoptic view provided by satellite remote sensing plays a crucial role.;
- Chapter 5 addresses simple digital image processing techniques. They exploit the potential of a multispectral approach to discriminate surface materials in various ways, especially to highlight those rock and sediment types that potentially may host groundwater.
- Chapter 6 shows how the digital analysis of topographic elevation data is able to model how water flows across the Earth’s surface. Combined with multi-wavelength image processing, this helps us visualise the relations between hydrology and geology, which are vital in siting surface water storage behind dams or in diverting flow to infiltrate and replenish groundwater reserves.
The second, practical part consists of four computer-based Exercises aimed at helping users to develop skills and experience in remote sensing and digital mapping. They cover the basic tools: displaying and enhancing image data; detecting different minerals; terrain and hydrological analysis; and making geological maps. These activities use a free version of the professional TNTmips software, which has much the same functions as other commercial packages, such as ENVI, ERDAS Imagine and Arcinfo. An Appendix guides users in acquiring globally available free or low-cost digital image data and preparing them for use in TNTmips.
On completing the course and with some practice users will be able independently to undertake their own water related projects to a professional standard. It is delivered free of charge (except for postage and packaging) on DVD, together with anaglyph viewers needed in Chapters 3 and 4 and the Exercises. Users are allowed to make copies of the DVD for distribution within their own institutions, subject to copyright restrictions (see below).
About the Author
During the catastrophic 1984-5 drought in the Horn of Africa I was a member of a team of geologists at the UK’s Open University (Seife Berhe, myself, Paul Gibson, Dave Rothery, John Taylor and Matthew Willis ) who assessed groundwater potential in the affected area, using whatever remotely sensed data were available. That experience spurred me to write a book to help spread geological remote-sensing skills. In three editions (1987; 1993; 2001) Image Interpretation in Geology covered all aspects of the geoscientific opportunities presented by remotely sensed data and the means of acquiring them. Over three decades I ran courses and workshops for FAO, the USGS Mission in Saudi Arabia, various NGOs working in the Horn of Africa, the Department of Mines and the Water Resources Department in Eritrea and in 2004 and 2006 for the International Committee of the Red Cross, nearly all on water-related reconnaissance mapping. Image Interpretation in Geology (3rd edition) is now out of print. Rather than develop a fourth edition of the book I decided to focus on what I had taught and learned about groundwater exploration since 1984 through a free computer- and web-based practical course: this is the outcome.
As well as the agencies with which I have worked, there have been far more individuals – facilitators, guides, drivers, field assistants, colleagues and, most important, the participants in my various teaching ventures – than can be listed here. Some individuals, however, I cannot forget because of their decisive support in many ways and what I have learned through engagement with them. It was Seife Berhe who motivated a group of remote sensers at the OU to make a practical response to the 1984-5 drought in the Horn of Africa, and with whom I worked in northern Eritrea under risky condition during 1988 and 1990, and later when that country’s independence struggle had ended. The late Jim Howard, Chief Engineer at Oxfam from 1965 to 1991, persuaded and funded Seife and me in 1988 to visit the war-torn areas we had analysed. Martine Bilanou of ERA got us back into the war zone in 1990 and supported teaching efforts in Asmara, Eritrea’s capital city, once peace had returned. Haile Woldetensae Hailemichael, Director of the Eritrean Water Resources Department until the late 1990’s, was effectively my ‘boss’ during visits to Eritrea from 1988 to 1994, but also a co-conspirator in bending a few rules and getting us into some, let’s say, ‘out-of-the-way’ places. Alem Kibreab, Michael Abraha (Eritrean Department of Mines), Tesfamichael Keleta (Eritrean Water Resources Department) and René Saameli (ICRC Water and Habitation Section) facilitated subsequent teaching and field work. From 1993 onwards I supervised two OU research students, Beto de Souza Filho and Margaret Andrews Deller, who both worked in Eritrea, Margaret also in Ethiopia, using advanced remote sensing techniques. Interactions with both of them concentrated the mind in various ways. A great many of the approaches used for teaching in this project resulted from many, usually lively, discussions and practical efforts centred on image processing with Margaret.
Finally, the Exercises on the DVD could not have been achieved without MicroImages of Lincoln, Nebraska, USA, who developed the advanced TNTgis software for geospatial analysis that forms the platform on which the Exercises are based. This use should not be regarded as my professional endorsement of TNTgis, and indeed there are a growing number of packages that your web browser will reveal by using the search term GIS software. My choice of TNTgis was because MicroImages provide a fully functional free version to aid in teaching digital image processing, GIS analysis and desktop mapping, albeit with a restriction on the sizes of data sets that may be used: in my experience no other commercial software house provides such a useful and generous option.
|This work is copyright ©2016 Stephen A. Drury. Some rights reserved.|
|Although free of charge, you may not:|
|Alter these files in any way, shape or form|
|Make and/or distribute copies of this work for personal or corporate profit.|
|The TNTmips Free® software is copyright ©2015 MicroImages, Inc|
|Note: The use of TNTmips Free in this course does not constitute an endorsement by the author|
|Additional anaglyph viewers can be ordered online from a variety of vendors (the anaglyphs in the course require red-cyan filters).|